Limit on rapid weight gain
Poultry breeding programs and farming practices have focused on achieving rapid growth and large breast muscles, largely ignoring health problems that arise from such rapid growth. Chickens raised for meat today can reach market weight in as little as 40 days. The average weight of a chicken today is 5.5 pounds, compared with 3.4 pounds in 1960.
Chickens often suffer from leg deformities and lameness due to their rapid growth and the weight of their large breast muscle. An estimated 90 million chickens raised for meat die each year before they reach the slaughterhouse due to their leg problems.
Rapid weight gain can also lead to problems with internal organs, especially the heart and lungs, which cannot distribute enough oxygen throughout the enlarged body's muscles. Fast-growing birds also often suffer from acute heart failure and Sudden Death Syndrome.
Rapid weight gain can be discouraged by setting a minimum age at slaughter or restricting the rate of growth.
Note: Rapid weight gain can also be prevented by choosing traditional breeds rather than "modern" breeds that have been bred to grow rapidly and have large breast muscles. Some programs encourage choosing breeds carefully but none prohibit modern breeds.
Limit on rapid weight gain: Criteria key
no minimum age at slaughter or restriction on rate of growth, but standards encourage traditional breeds or breeds with low mortality levels
minimum age at slaughter is at least 60 days, or rate of growth restricted to no more than 0.083 pounds per day
minimum age at slaughter is at least 80 days, or rate of growth restricted to no more than 0.063 pounds per day
Limit on rapid weight gain: How labels stack up against criteria